Any chip that connect to your maf,or air temp sensor is simply a resistor.The only real thing for most mercedes,is mail you computer to be chipped,about $500.You can on gasoline engines advance timing be using 1.1k resistor between temp sensor to computer.Diesels nneed larger volume injectors,and a pump that will fill them,and if electronic,a updated program.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran